Arvo building, Jarmo Visakorpi auditorium, address: Lääkärinkatu 1
Doctoral defence of M.Sc. Jissa Vinoda Thulaseedharan
The field of science of the dissertation is Epidemiology.
The opponent is professor (emerita) Marjukka Mäkelä (University of Copenhagen, Denmark). Professor Nea Malila acts as the custos.
The language of the dissertation defence is English.
Evaluation of Sociodemographic, Reproductive and Screening-related Factors on Risk of and Survival from Cervical Cancer in Rural South India
Cervical cancer incidence and survival widely varies between and within countries. Low socioeconomic
status is associated with higher risk of cervical cancer as well as with poor survival. A single visit approach of visual inspection with acetic acid (VIA) combined with cryotherapy is established as an effective screening method in reducing cervical cancer incidence and mortality in low-resource settings. The study evaluated the long-term risk of cervical cancer among visually screened women with different triage methods, histological findings and treatment options; and explored limitations of colposcopy triage in screen and treat programmes in low-resource settings. The study also evaluated the role of sociodemographic and reproductive factors in the risk of and survival from cervical cancer, and the bias in using screening data to study the sociodemographic and reproductive risk factors and prognostic factors of cervical cancer.
The research was based on a large cervical cancer screening trial by visual inspection with acetic acid (VIA) conducted during 2000-2003 in a rural population of Tamil Nadu state, India. All screen positive (n=3021) and negative (n=28255) women except 67 screen-detected cervical cancer patients were followed until December 2012 to assess long-term risk of cervical cancer among VIA screened women. Sociodemographic and reproductive risk factors were determined using data from control arm, and the survival and its socioeconomic determinants were studied among women diagnosed with cervical cancer during 2000 to 2006 in control arm. Bias in the use of screening data to study sociodemographic and reproductive risk factors was explained using data from both control (n=30958) and intervention arm (n=49311) followed until December 2006. Bias in the use of screening data to study sociodemographic prognostic factors was explained using 67 screen-detected women and 165 women diagnosed with cervical cancer from control arm during 2000-2006 and followed until December 2012.
The study showed a high negative predictive value for VIA even after 12 years of screening. Compared to VIA negative women, women who were with VIA positive but colposcopy negative and who had no histological confirmation showed a hazard ratio for cervical cancer of 6.5 (95%CI: 1.6 to 27.1). VIA positive women with no colposcopic evaluation or who had an inconclusive colposcopy and had no histological confirmation showed the highest risk for cervical cancer (HR= 20.7, 95%CI: 5 to 85.3).
Women with older age (50-59 years), no education and higher number of pregnancies (4+) showed a significant higher risk for cervical cancer compared to women with younger age, some education, and less than four pregnancies respectively in the control population. Hazard ratios of sociodemographic and reproductive risk factors varied accordingly with study group and screening status.
The benefit in terms of achieving substantial incidence reduction as a result of screening was acquired by younger, uneducated, currently married and women living in tiled or concrete houses. The observed five-year survival was 32.5% among women diagnosed with cervical cancer from control arm. Stage of disease was the most important determinant of survival (adjusted HR for mortality for stage 2 or worse cancers: 3.9; 95% CI: 1.7 to 9.1 when stage1 cancers were the reference). Observed five year survival was 47.6% among screen detected women. Variation in survival by age at diagnosis was substantial in screen-detected women. In addition, the variation in survival between uneducated and educated women was reduced in screen-detected women.
The results from the study indicate that self-selection in attendance and screening itself will bias the effect estimates of risk factors, whereas selection bias and over diagnosis will bias effect estimates of prognostic factors while using screening data to study the sociodemographic and reproductive risk and prognostic factors. In a controlled screening trial, the data from control population would be ideal for studying the sociodemographic and reproductive risk and prognostic factors, and the results should be interpreted with caution if estimates are derived using screening data. The study demonstrated that a screen and treat policy without colposcopy triage will be a more effective strategy in low-resource settings. Level of education and age of women are both important factors to be considered while implementing screening, further diagnosis, treatment and follow-up in order to achieve better health outcome in low-resource settings. Creating awareness about cervical
cancer through educational programmes, improvements in living standards and assuring accessibility to an efficient health care system can altogether play an important role in reducing the burden of cervical cancer in rural populations.
The dissertation is published in the publication series of Acta Universitatis Tamperensis; 2263, Tampere University Press, Tampere 2017. The dissertation is also published in the e-series Acta Electronica Universitatis Tamperensis; 1764, Tampere University Press 2017.